Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-10-18T00:00:00 kernel: net: atl1c: fix soft lockup on out-of-range tpd_cons read 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-835

In the Linux kernel, the following vulnerability has been resolved: net: atl1c: fix soft lockup on out-of-range tpd_cons read The hardware can report an out-of-range tpd_cons (seen as 0xffff) while the PCIe link/MAC is resetting. An out-of-range value can never be reached and the loop below would spin forever. To avoid a soft lockup treat it as "nothing new to clean" instead. Reproduced on two machines, same NIC (Qualcomm Atheros AR8151 v2.0, 4-port), triggered by rebooting a Mikrotik CCR2004 PCIe card that the ports are directly linked to: - Ubuntu 26.04.1 LTS, kernel 7.0.0-31-generic. The link-flap precursor, before the lockup was captured with a full trace elsewhere: atl1c 0000:05:00.0 enp5s0f0: NETDEV WATCHDOG: CPU: 4: transmit queue 2 timed out 489984 ms atl1c 0000:05:00.0: MAC state machine can't be idle since disabled for 10ms second atl1c 0000:05:00.0: atl1c: enp5s0f0 NIC Link is Up<65535 Mbps Full Duplex> 65535 (0xffff) here is the same value tpd_cons reads back once the loop below gets stuck. - Proxmox VE, kernel 7.0.14-11-pve. Same NIC/trigger, this time caught by the soft lockup watchdog with a full stack trace: watchdog: BUG: soft lockup - CPU#12 stuck for 354s! [napi/eth%d-0:329] CPU: 12 UID: 0 PID: 329 Comm: napi/eth%d-0 Tainted: P O L 7.0.14-11-pve #1 PREEMPT(lazy) RIP: 0010:atl1c_clean_tx+0x142/0x2d0 [atl1c] Call Trace: <TASK> __napi_poll+0x32/0x1e0 napi_threaded_poll_loop+0x286/0x2e0 napi_threaded_poll+0xfd/0x140 kthread+0xf7/0x130 ret_from_fork+0x2da/0x3a0 ret_from_fork_asm+0x1a/0x30 </TASK>

A flaw was found in the Linux kernel's atl1c network driver. When an interface experiences a link reset or link flapping, the hardware can return an out-of-range descriptor value that the driver fails to validate. An adjacent entity capable of triggering network link state changes can exploit this behavior, causing the transmit cleanup routine to enter an infinite loop. This failure locks up the CPU, resulting in a Denial of Service (DoS).

This vulnerability is rated as Moderate impact because exploitation requires the host to possess specific Qualcomm Atheros network hardware and is restricted to adjacent network vectors. While an adjacent actor capable of forcing link renegotiation can induce an unrecoverable kernel soft lockup that disrupts system availability, the issue cannot lead to unauthorized data disclosure or code execution. Furthermore, enterprise server platforms rarely employ these consumer-grade Ethernet controllers, substantially limiting real-world exposure across standard Red Hat deployments. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Fix deferred kernel Red Hat Enterprise Linux 7 Fix deferred kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-98489 https://nvd.nist.gov/vuln/detail/CVE-2026-98489 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98489.mbox